Droplet separators are known in which flow passages are provided between the inlet and outlet sides of a stack of corrugated plates whose corrugations define the flow passages betweem them. Such flow passages are of the direction-change type in which two or more bends are provided for deflecting the gas stream first to one side and then to another so that the droplets collect on the walls of the flow passages by reason of the direction change and because of their inertia and are removed from the gas stream.
Where two adjacent plates join, the flow passages or, more specifically, the flanks thereof and hence flanks of the troughs of the corrugations, meet in a gusset or crevice which acts as a collecting channel for the liquid and permits the liquid collected on the walls of the flow passage to run off.
The corrugations may all be of a given wavelength and amplitude. The term "wavelength" is used herein to refer to the transverse distance between two corresponding points for each pair of successive corrugations, each corrugation being understood to include a trough and a crest. The term "amplitude" is used herein to refer to the height of the crest or the depth of the trough, i.e. the dimension of the corrugation as measured perpendicular to a median plane lying midway between the tops of said crests and bottom of a trough between a pair of crests.
The amplitude and wavelength is selected in accordance with the quantity of gas to traverse the stack in a given time and thus in accordance with the flow velocity. Another factor in dimensioning the corrugations is the droplet loading of the gas stream, i.e. the quantity of liquid contained or entrained in the gas stream, and the limiting droplet size for separation, i.e. the limiting separation particle size. The limiting separation particle size is the smallest droplet size for which 100% removal is assured.
Naturally, the dimensions must be selected in accordance with these parameters such that the gas stream has the smallest possible pressure drop across the stack. It is self-understood that the stack may include and, as a rule, does include a straight inlet portion for each of the flow passages and a straight outlet portion parallel to the straight inlet portion. Between these inlet and outlet portions, the flow passages are provided with the aforementioned bends.
A particle separator of this type and of the type of the present invention can be used effectively for the removal of liquid droplets of all types from gas streams of all compositions. For example, such droplet separators are provided downstream of gas washing systems to recover liquid from the gas before the gas is admitted, for example, to an expansion turbine or released into the atmosphere.
In one prior-art system of the type described previously (see U.S. Pat. No. 2,555,125) the corrugations are more or less precisely sinusoidal in cross section. As a result, the contact locations between the crests of adjacent plates define practically line-contact patterns. The resulting gusset or runoff channel is thus fairly narrow and has been found to introduce problems.
Furthermore, the conventional unit, for a given amplitude and wavelength has been found to be incapable of sustaining extremely high input flow velocities without detrimentally affecting the separation. In other words, as the input velocity of the gas increases, the separation efficiency drops.
Furthermore, the limiting droplet size of such a system is generally relatively large. In other words small droplets are not effectively removed by the unit.
This is especially the case when, for structural purposes or otherwise, the flow passages are partitioned by walls which run orthogonal to the amplitude of the corrugations centrally through the flow passages.